Short tandem repeats (STRs) are commonly used for the analysis of DNA in a range of forensic applications, such as the analysis of DNA found at crime scenes. STRs found on the Y chromosome (Y-STRs) are used in determining the presence of male DNA in samples that may also contain female DNA, such as those obtained in sexual assault cases.
Many Y-STRs are unable to distinguish between related males sharing the same paternal lineage. Since mutations in these Y-STRs are relative rare events, the majority of these will be shared between such male relatives.
Certain Y-STRs have been identified as “rapidly mutating”, which for the present purposes indicates that they have mutation rates in the order of 10−2 whereas all the other Y STRs have a mutation rates in the order of 10−3. The use of these markers for identification allows distinctions to be made between even closely related male subjects.